Adjustable fragmentation in laser desorption/ionization from laser-induced silicon microcolumn arrays

Area of Science:

• Materials Science
• Analytical Chemistry
• Surface Science

Background:

• Matrix-free substrates are desirable for soft laser desorption/ionization mass spectrometry (SLDI-MS) to simplify sample preparation and analysis.
• Developing novel substrates with controlled morphology is crucial for enhancing ionization efficiency and sensitivity in mass spectrometry.

Purpose of the Study:

• To develop and characterize laser-induced silicon microcolumn arrays (LISMA) as matrix-free substrates for SLDI-MS.
• To investigate the influence of processing environments (air, SF6, water) on microcolumn morphology and SLDI-MS performance.
• To evaluate the sensitivity, mass range, and sequencing capabilities of LISMA for peptides and polymers.

Main Methods:

• Fabrication of silicon microcolumn arrays by irradiating silicon wafers with a mode-locked Nd:YAG laser in different environments (air, SF6, water).
• Characterization of microcolumn tip radii of curvature using microscopy.
• Application of LISMA as matrix-free substrates in SLDI-MS experiments using a nitrogen laser.
• Analysis of ion yield, threshold laser fluence, mass range, and in-source decay for peptide and polymer analysis.

Main Results:

• LISMA were successfully fabricated with varying column tip radii depending on the processing environment (water: ~120 nm, SF6: <1 µm, air: ~2 µm).
• Microcolumn arrays processed in water demonstrated superior performance in SLDI-MS, yielding molecular ions for peptides and polymers at low laser fluence.
• Achieved low-femtomole sensitivity and a mass range of approximately 6000 Da, comparable to matrix-assisted laser desorption/ionization.
• Extensive peptide sequence information was obtained via in-source decay at elevated laser fluences.

Conclusions:

• Laser-induced silicon microcolumn arrays (LISMA) are effective matrix-free substrates for SLDI-MS.
• The processing environment significantly influences microcolumn morphology and SLDI-MS performance, with water-processed arrays showing the best results.
• LISMA offer high sensitivity, broad mass range, and valuable sequencing capabilities, attributed to their unique submicrometer morphology and material properties.